Sterilizable Polymer Flow Cell with Detachable Ultrasonic Transducers
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Solution Overview
Problem
Existing ultrasonic flow meters are not suitable for systems used in the analysis, purification, or preparation of bio molecules like proteins and nucleic acids, as they lack the required accuracy and are not compatible with changing fluid compositions, and they often require recalibration and are not suitable for disposable systems.
Innovation Solution
A polymer-based flow cell with axially aligned ultrasonic transducers that are reversibly detachable, made from low-damping materials like polymethylpentene, ensuring high accuracy and minimal backpressure, and designed for disposable use with sterilization capabilities, such as gamma irradiation, to meet the needs of pharmaceutical applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional clamp-on ultrasonic flow meters are used with external transducers, then the measurement can be performed without perturbing the fluid flow, but the angle of refraction at the conduit-fluid interface is small resulting in low sensitivity to flow rate
Solution Approach 1:
The patent introduces an acoustic matching layer as an intermediary between the transducer and the fluid. This layer has acoustic impedance intermediate between the transducer material and the fluid, improving acoustic coupling and enabling more effective transmission of ultrasonic waves into the fluid. This resolves the contradiction by enhancing measurement precision through better acoustic coupling while maintaining the non-intrusive clamp-on configuration for reliability.
Solution Approach 2:
The patent transitions from traditional longitudinal wave transmission to using shear waves that are mode-converted at the interface. By changing the dimension of wave motion from longitudinal to shear polarization and utilizing mode conversion at the conduit-fluid interface, the ultrasonic waves achieve a much higher transmission angle (typically twice that of longitudinal waves), thereby improving sensitivity to flow rate while maintaining accurate measurement.
2Ease of operation
If clamp-on ultrasonic flow meters are used with external transducers, then the transducer positioning is simplified, but the angle of refraction varies with fluid composition changes making the measurements inaccurate for systems with changing fluid compositions
Solution Approach 1:
The patent employs shear waves instead of traditional longitudinal waves, fundamentally changing the physical parameter of wave motion. Shear waves are mode-converted at the conduit-fluid interface to produce longitudinal waves at a much higher angle. This parameter change makes the measurement less sensitive to variations in fluid composition, as the mode conversion process and higher transmission angle compensate for changes in acoustic properties, thereby maintaining measurement precision while preserving ease of transducer positioning.
3Strength
If ultrasonic transducers are permanently attached to the flow cell, then the assembly is more robust, but the flow cell cannot be easily sterilized or replaced for disposable use
Solution Approach 1:
The patent divides the ultrasonic flow meter into separate modular components: the flow cell and the transducers are detachable from each other. This segmentation allows the flow cell to be easily sterilized or replaced as a disposable component, while the transducers can be reused on different flow cells. The modular design maintains robust connections during use while enabling easy separation for sterilization or disposal, resolving the contradiction between attachment strength and adaptability.
4Productivity
If the flow cell channel has complex geometry to accommodate various flow rates, then the flow meter can handle a wide range of flow rates, but the bandbroadening effect increases reducing measurement accuracy
Solution Approach 1:
The patent uses an adjustable ultrasonic beam angle achieved through the shear wave mode conversion mechanism. By dynamically adjusting the beam angle, the system can optimize the measurement path for different flow rates without requiring complex channel geometry. This dynamic adjustment capability allows the flow cell to maintain a simple, straight channel design that minimizes bandbroadening while still accommodating a wide range of flow rates, resolving the contradiction between productivity and measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The flow cell provides accurate flow rate measurements with less than 5% error across a wide range, minimal backpressure, and reduced bandbroadening, allowing for efficient use in chromatography and filtration processes without the need for frequent recalibration, and is suitable for disposable systems in pharmaceutical applications.
Implementation Method 1
two transducers (11) of ultrasonic waves axially aligned with each other on opposite sides of said channel (13) wherein the ultrasonic waves transmitted by said transducers travel longitudinally in opposite directions
Implementation Method 2
the flow cell with the transducers detached is made of a polymeric material... characterized by low damping of ultrasonic waves
Implementation Method 3
sterilisable, for example by the use of gamma irradiation
Data Source
AI summary
The invention relates to a flow cell for an ultrasonic flow meter comprising two transducers of ultrasonic waves wherein the two transducers are reversibly detachable from the flow cell. The flow cell with the transducers detached is sterilisable and is particularly suitable for use in disposable or single-use systems.